Electromagnetic chuck for OLED mask chucking

ABSTRACT

An electromagnetic mask chuck is described herein. The electromagnetic mask chuck includes a body with a plurality of electromagnets formed therein. The electromagnets can then deliver a magnetic force to a mask to position and hold the mask over or on the substrate for further deposition. The electromagnets are controlled using a power source, to deliver a controlled magnetic field to the mask.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 62/006,853, filed Jun. 2, 2014, which is herein incorporated byreference.

BACKGROUND

1. Field

Embodiments of the present disclosure generally relate to a substratesupport, and more particularly, a substrate carrier with anelectromagnetic mask chuck suitable for use in a vertical and otherprocessing systems.

2. Description of the Related Art

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. As well, the inherent properties of organicmaterials, such as their flexibility, may be advantageous for particularapplications such as for deposition or formation on flexible substrates.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors.

For OLEDs, the organic materials are believed to have performanceadvantages over conventional materials. For example, the wavelength atwhich an organic emissive layer emits light may generally be readilytuned with appropriate dopants. OLEDs make use of thin organic filmsthat emit light when voltage is applied across the device. OLEDs arebecoming an increasingly interesting technology for use in applicationssuch as flat panel displays, illumination, and backlighting.

The substrates as well as a fine metal mask are often held on asubstrate carrier using mechanical force. Conventional mechanicalcontacts used to hold the substrate and the mask during processing mayoften result in substrate damage due to the high mechanical forceapplied. The mechanical force is further applied to hold the fine metalmask in place during processing. The conventional mechanical carriersgenerally hold the substrate at the edges, thus resulting in a highlyconcentrated physical contact at the edges of the substrate so as toensure sufficient clamping force applied to securely pick up thesubstrate. This mechanical contact concentrated at the edges of thesubstrate inevitably creates contact contamination or physical damage,undesirably degrading the substrate.

Newer processing systems have incorporated alternative mechanisms forchucking the substrate to avoid the above described damage, such asholding the substrate in place using electrostatic force. Electrostaticforce can effectively hold the substrate in position during processingwhile minimizing contact between metal components of the system and thesubstrate. However, using electrostatic force to chuck the mask inposition on the substrate has proven to be very challenging.

Therefore, there is a need for a method and apparatus for securelypositioning a mask independently of the substrates in a processingsystem.

SUMMARY

The present disclosure provides an electromagnetic mask chuck andmethods for using the same. The electromagnetic mask chuck can beintegrated into a process chamber or a substrate carrier for use in aprocess chamber. By incorporating a series of electromagnets, a mask anda substrate can be chucked to the substrate carrier in a controlledfashion.

In one embodiment, a processing system is described. The processingsystem can include a process chamber configured to receive a substratecarrier holding a substrate, and to deposit a material on the substratewhile on the substrate carrier. The processing system can furtherinclude an electromagnetic mask chuck positioned in the process chamber.The electromagnetic mask chuck can include a plurality of electromagnetsoperable to chuck a mask to the substrate through the substrate carrier.

In another embodiment, a substrate carrier for use in a process chamberis described. The substrate carrier can include a support baseconfigured to transport a substrate into and out of the processingchamber, the support base having a substrate supporting surface. Thesubstrate carrier can further include an electromagnetic mask chuckcoupled to the support base, The electromagnetic mask chuck can includea plurality of electromagnets operable to chuck a mask to the substratethrough the substrate carrier.

In another embodiment, a method for chucking a mask in a process chamberis described. The method can include transferring a substrate disposedon a substrate supporting surface of a substrate carrier into a processchamber. The substrate carrier can then be positioned in a processingposition within the process chamber. Then, a mask is electromagneticallychucked to the substrate disposed on the substrate carrier. Then a layeris deposited through the mask onto the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1A to 1D show schematic views illustrating an evaporation sourcefor organic material in use with a magnetic chucking assembly, accordingto embodiments described herein;

FIG. 2 shows a schematic top view of a deposition apparatus with amagnetic chucking assembly according to embodiments described herein;

FIG. 3 depicts an exploded view of one embodiment of a substrate carrierplate with integrated electrostatic chuck in a substrate carrieraccording to an embodiment;

FIG. 4A depicts a chucking assembly with an electromagnetic mask chuck,according to an embodiment; and

FIGS. 4B-4E depict electromagnetic mask chucks useable with a chuckingassembly, according to embodiments described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

The present disclosure generally relates to an electromagnetic maskchuck and methods for using the same. The electromagnetic mask chuck canbe integrated into a process chamber or a substrate carrier for use in aprocess chamber. By incorporating a series of electromagnets, the maskand the substrate can be chucked to the substrate carrier in acontrolled fashion.

FIGS. 1A to 1D show an evaporation source 100 in various positions in avacuum chamber 110 with respect to a first mask 132 a and a second mask132 b, according to embodiments described herein. The movement of theevaporation source 100 between the different positions is indicated byarrows 101B, 101C, and 101D. FIGS. 1A to 1D show the evaporation source100 having an evaporation crucible 104 and the distribution pipe 106.The distribution pipe 106 is supported by the support 102. Further,according to some embodiments, the evaporation crucible 104 can also besupported by the support 102. The substrates, e.g. a first substrate 121a and a second substrate 121 b, are provided in the vacuum chamber 110.The first substrate 121 a and the second substrate 121 b are supportedand chucked by a respective substrate carrier, e.g. a first substratecarrier 150 a and a second substrate carrier 150 b, described in moredetail with reference to FIG. 3 below. The first mask 132 a and secondmask 132 b are provided between the substrate 121 and the evaporationsource 100. The first mask 132 a and second mask 132 b are chucked by arespective mask chucking assembly, e.g. a first mask chucking assembly151 a and a second mask chucking assembly 151 b, described in moredetail with reference to FIG. 4A to 4E below. As illustrated in FIGS. 1Ato 1D, organic material is evaporated from the distribution pipe 106 todeposit a layer on the substrates. The first mask 132 a and the secondmask 132 b mask the substrate during the layer deposition. This isindicated by reference numeral 10.

In FIG. 1A, the evaporation source 100 is shown in the first positionwith the first substrate carrier 150 a and the second substrate carrierbeing active. As shown in FIG. 1B, the first chucking assembly 150 a hasthe first substrate 121 a chucked in position. The first mask 132 a,shown positioned over the first substrate 121 a, is chucked intoposition by the first mask chucking assembly 151 a over the appropriateportion of the first substrate 121 a. With the first mask 132 a inposition, the first substrate 121 a in the vacuum chamber 110 isdeposited with a layer of organic material by a translational movementof the evaporation source as indicated by arrow 101B. While the firstsubstrate 121 a is deposited with the layer of organic material throughthe first mask 132 a, a second substrate 121 b, e.g. the substrate onthe right-hand side in FIGS. 1A to 1D, can be exchanged. FIG. 1B shows asecond transportation track 124 b for the second substrate 121 b. As thesecond substrate 121 b is not in position in FIG. 1B, the secondsubstrate carrier 150 b and the second mask chucking assembly 151 b arenot activated for chucking. After the first substrate 121 a has beendeposited with the layer of organic material, the distribution pipe 106of the evaporation source 100 is rotated as indicated by arrow 101C inFIG. 1C.

During deposition of the organic material on the first substrate 121 a,the second substrate 121 b is then chucked to the second substratecarrier 150 b. The second mask 132 b is then positioned and aligned withrelation to the second substrate followed by chucking the second mask132 b to the second mask chucking assembly 151 b over the secondsubstrate 121 b. Accordingly, after the rotation shown in FIG. 1C, thesecond substrate 121 b can be coated with a layer of organic materialthrough the second mask 132 b as indicated by arrow 101D. While thesecond substrate 121 b is coated with the organic material, the firstmask 132 a can be unchucked from the first mask chucking assembly 151 a.With the first mask 132 a being unchucked, the first substrate 121 a canthen be removed from the chamber for unchucking from the first chuckingassembly 150 a. FIG. 1D shows a first transportation track 124 a in theposition of the first substrate 121 a.

According to embodiments described herein, the first substrate 121 a andsecond substrate 121 b are coated with organic material in asubstantially vertical position. That is, the views shown in FIGS. 1A to1D are top views of an apparatus including the evaporation source 100.The distribution pipe can be a vapor distribution showerhead,particularly a linear vapor distribution showerhead. Thereby, thedistribution pipe provides a line source extending essentiallyvertically. According to embodiments described herein, which can becombined with other embodiments described herein, essentially verticallyis understood particularly when referring to the substrate orientation,to allow for a deviation from the vertical direction of 10° or below.This deviation can be provided because a substrate carrier with somedeviation from the vertical orientation might result in a more stablesubstrate position. Yet, the substrate orientation during deposition ofthe organic material is considered essentially vertical, which isconsidered different from the horizontal substrate orientation. Thesurface of the substrates is thereby coated by a line source extendingin one direction corresponding to one substrate dimension and atranslational movement along the other direction corresponding to theother substrate dimension. Moreover, though described in reference to avertical position for an exemplary vertical process chamber, thisconfiguration and/or chamber is not intended to be limiting. Embodimentsdescribed herein are equally amenable to horizontal chambers or chamberswhich can process more or fewer substrates.

Embodiments described herein particularly relate to deposition oforganic materials, e.g. for OLED display manufacturing and on large areasubstrates. According to some embodiments, large area substrates orcarriers supporting one or more substrates, i.e. large area carriers,may have a size of at least 0.174 m². The size of the carrier can beabout 1.4 m² to about 8 m², more typically about 2 m² to about 9 m² oreven up to 12 m². The rectangular area, in which the substrates aresupported, for which the holding arrangements, apparatuses, and methodsaccording to embodiments described herein are provided, can be carriershaving sizes for large area substrates as described herein. Forinstance, a large area carrier, which would correspond to an area of asingle large area substrate, can be GEN 5, which corresponds to about1.4 m² substrates (1.1 m×1.3 m), GEN 7.5, which corresponds to about4.29 m² substrates (1.95 m×2.2 m), GEN 8.5, which corresponds to about5.7 m² substrates (2.2 m×2.5 m), or even GEN 10, which corresponds toabout 8.7 m² substrates (2.85 m×3.05 m). Even larger generations such asGEN 11 and GEN 12 and corresponding substrate areas can similarly beimplemented. According to typical embodiments, which can be combinedwith other embodiments described herein, the substrate thickness can befrom 0.1 to 1.8 mm and the holding arrangement, and particularly theholding devices, can be adapted for such substrate thicknesses. However,particularly the substrate thickness can be about 0.9 mm or below, suchas 0.5 mm or 0.3 mm, and the holding arrangement, and particularly theholding devices, are adapted for such substrate thicknesses. Thesubstrate may be made from any material suitable for materialdeposition. For instance, the substrate may be made from a materialselected from the group consisting of glass (for instance soda-limeglass, borosilicate glass etc.), metal, polymer, ceramic, compoundmaterials, carbon fiber materials or any other material or combinationof materials which can be coated by a deposition process.

According to embodiments described herein, the first mask chuckingassembly 151 a and the second mask chucking assembly 151 b employelectromagnets to allow independent chucking and unchucking of themasks, e.g. the first mask 132 a and the second mask 132 b, withoutaffecting the chucking of the respective substrates, e.g. the firstsubstrate 121 a and the second substrate 121 b. In FIGS. 1A and 1B, theelectromagnets in connection with the first chucking assembly 150 a areactivated by receiving power from a power source (not shown). In FIGS.1C and 1D, the electromagnets in connection with the second chuckingassembly 150 b are activated by receiving power from the power source.Further, the mask chucking assemblies according to embodiments describedherein can minimize and reduce the force of contact between thesubstrate and the mask during OLED display manufacturing. The first maskchucking assembly 151 a and the second mask chucking assembly 151 b canbe integrated into the process chamber or with the substrate carrier.Embodiments which can be integrated into the process chamber include theembodiments described with reference to FIGS. 4A-4D. Embodiments whichcan be integrated with the substrate carrier include the embodimentsdescribed with reference to FIG. 4E.

FIG. 2 illustrates an embodiment of a deposition apparatus 200 fordepositing organic material in a vacuum chamber 240 including thesubstrate carrier 150 a and 150 b and a mask chucking assembly 151 a and151 b, according to one embodiment. The evaporation source 230 isprovided in the vacuum chamber 240 on a track or linear guide 224. Thelinear guide 224 is configured for the translational movement of theevaporation source 230. Thereby, according to different embodiments,which can be combined with other embodiments described herein, a drivefor the translational movement can be provided in the evaporation source230, at the track or linear guide 224, within the vacuum chamber 240 ora combination thereof. FIG. 2 shows a valve 205, for example a gatevalve. The valve 205 allows for a vacuum seal to an adjacent vacuumchamber (not shown). The valve can be opened for transport of aplurality of substrates, shown here as substrates 121 a and 121 b, orone or more masks for the plurality of substrates, shown here as masks132 a and 132 b, into the vacuum chamber 240 or out of the vacuumchamber 240.

According to some embodiments, which can be combined with otherembodiments described herein, a further vacuum chamber, such asmaintenance vacuum chamber 210 is provided adjacent to the vacuumchamber 240. Thereby the vacuum chamber 240 and the maintenance vacuumchamber 210 are connected with a valve 207. The valve 207 is configuredfor opening and closing a vacuum seal between the vacuum chamber 240 andthe maintenance vacuum chamber 210. The evaporation source 230 can betransferred to the maintenance vacuum chamber 210 while the valve 207 isin an open state. Thereafter, the valve can be closed to provide avacuum seal between the vacuum chamber 240 and the maintenance vacuumchamber 210. If the valve 207 is closed, the maintenance vacuum chamber210 can be vented and opened for maintenance of the evaporation source230 without breaking the vacuum in the vacuum chamber 240.

Two substrates 121 a and 121 b can be supported on respectivetransportation tracks within the vacuum chamber 240. Further, two tracksfor providing masks 132 a and 132 b thereon can be provided. Thereby,coating of the substrates 121 a and 121 b can be masked by respectivemasks 132 a and 132 b. According to typical embodiments, the masks 132 aand 132 b are provided in a mask frame 131 a and 131 b to hold the masks132 a and 132 b in a predetermined position. The masks 132 a and 132 bare chucked into position over the substrate 121 a and 121 b using thechucking assembly 150 a and 150 b. The chucking assembly 150 a and 150 bcan act independently to chuck the substrate 121 a and 121 b and themasks 132 a and 132 b, such that the masks 132 a and 132 b can bepositioned over the substrate 121 a and 121 b without affecting thepositioning of the substrate 121 a and 121 b and without mechanicalcontrol of the masks 132 a and 132 b.

According to some embodiments, which can be combined with otherembodiments described herein, a substrate 121 a and 121 b can besupported by a substrate chucking assemblies 150 a and 150 b, which areconnected to respective alignment units 212 a and 212 b. The alignmentunits 212 a and 212 b can adjust the position of the substrate 121 a and121 b with respect to the masks 132 a and 132 b. FIG. 2 illustrates anembodiment where the substrate chucking assemblies 150 a and 150 b areconnected to the alignment unit 212. Accordingly, the substrate 121 aand 121 b are moved relative to the masks 132 a and 132 b in order toprovide for a proper alignment between the substrate 121 a and 121 b andthe masks 132 a and 132 b during deposition of the organic material.According to a further embodiment, which can be combined with otherembodiments described herein, alternatively or additionally the masks132 a and 132 b and/or the mask frame 131 a and 131 b holding the masks132 a and 132 b can be connected to the alignment unit 212. Thereby,either the masks 132 a and 132 b can be positioned relative to thesubstrate 121 a and 121 b or the masks 132 a and 132 b and the substrate121 a and 121 b can both be positioned relative to each other. Thealignment units 212, which are configured for adjusting the relativeposition between a substrate 121 a and 121 b and masks 132 a and 132 brelative to each other, allow for a proper alignment of the maskingduring the deposition process, which is beneficial for high quality orLED display manufacturing.

Examples of an alignment of a mask and a substrate relative to eachother include alignment units, which allow for a relative alignment inat least two directions defining a plane, which is essentially parallelto the plane of the substrate and the plane of the mask. For example, analignment can at least be conducted in an x-direction and a y-direction,i.e. two Cartesian directions defining the above-described parallelplane. The mask and the substrate can be essentially parallel to eachother. Specifically, the alignment can further be conducted in adirection essentially perpendicular to the plane of the substrate andthe plane of the mask. Thus, an alignment unit is configured at leastfor an X-Y-alignment, and specifically for an X-Y-Z-alignment of themask and the substrate relative to each other. One specific example,which can be combined with other embodiments described herein, is toalign the substrate in x-direction, y-direction and z-direction to amask, which can be held stationary in the vacuum chamber 240.

As shown in FIG. 2, the linear guide 224 provides a direction of thetranslational movement of the evaporation source 230. On both sides ofthe evaporation source 230 and masks 132 a and 132 b are provided. Themasks 132 a and 132 b can thereby extend essentially parallel to thedirection of the translational movement. Further, the substrates 121 aand 121 b at the opposing sides of the evaporation source 230 can alsoextend essentially parallel to the direction of the translationalmovement. According to typical embodiments, a substrate 121 a and 121 bcan be moved into the vacuum chamber 240 and out of the vacuum chamber240 through valve 205. Thereby, and deposition apparatus 200 can includea respective transportation track for transportation of each of thesubstrates 121 a and 121 b. For example, the transportation track canextend parallel to the substrate position shown in FIG. 2 and into andout of the vacuum chamber 240.

Typically, further tracks are provided for supporting the mask frames131 a and 131 b and thereby the masks 132 a and 132 b. Accordingly, someembodiments, which can be combined with other embodiments describedherein, can include four tracks within the vacuum chamber 240. In orderto move one of the masks 132 a and 132 b out of the chamber, for examplefor cleaning of the mask, the mask frame 131 a and 131 b and, thereby,the mask can be moved onto the transportation track of the substrate 121a and 121 b. The respective mask frame can then exit or enter the vacuumchamber 240 on the transportation track for the substrate. Even thoughit would be possible to provide a separate transportation track into andout of the vacuum chamber 240 for the mask frames 131 a and 131 b, thecosts of ownership of a deposition apparatus 200 can be reduced if onlytwo tracks, i.e. transportation tracks for a substrate, extend into andout of the vacuum chamber 240 and, in addition, the mask frames 131 aand 131 b can be moved onto a respective one of the transportationtracks for the substrate by an appropriate actuator or robot.

Once the masks 132 a and 132 b and the substrates 121 a and 121 b arepositioned in alignment with one another, the chucking assemblies 150 aand 150 b can bring the masks 132 a and 132 b into close proximity tothe substrates 121 a and 121 b. During the deposition process, anorganic material is being propelled at the substrates 121 a and 121 bfrom the evaporation source 230. This organic material is depositedthrough formations in the masks 132 a and 132 b, onto the substrates 121a and 121 b. The formations provide the subsequent shape of thedeposited material on the substrates 121 a and 121 b. If the masks 132 aand 132 b are positioned too far from the substrates 121 a and 121 b,the organic material will be deposited imprecisely through theformations in the masks 132 a and 132 b leading to poor resolution orfailure of the final product. If the masks 132 a and 132 b make too muchcontact or uncontrolled contact with the substrates 121 a and 121 b, themasks 132 a and 132 b can cause physical damage to the substrates 121 aand 121 b. This proximity damage can be exacerbated by multiplealignment processes between the substrates 121 a and 121 b and the masks132 a and 132 b. By using the chucking assemblies 150 a and 150 b asdescribed herein, the three dimensional position of the mask can be morefinely controlled allowing for better deposition with minimal risk ofsubstrate damage during processing.

FIG. 2 illustrates another exemplary embodiment of the evaporationsource 230. The evaporation source 230 includes a support 104. Thesupport 104 is configured for the translational movement along thelinear guide 224. The support 104 supports an evaporation crucible 106and a distribution pipe 208 provided over the evaporation crucible 106.Thereby, the vapor generated in the evaporation crucible can moveupwardly and out of the one or more outlets of the distribution pipe.According to embodiments described herein, the distribution pipe 208 canalso be considered a vapor distribution showerhead, for example a linearvapor distribution showerhead.

FIG. 2 further illustrates a shield assembly having at least one shield202. As shown in FIG. 2, embodiments can include two shields 202, e.g.side shields. Thereby, an evaporation of the organic material can bedelimited in the direction towards the substrate. An evaporationsideward relative to the distribution pipe, i.e., in a direction that isfor example perpendicular to the normal evaporation direction, can beavoided or used in an idle mode only. In light of the fact that it canbe easier to block the vapor beam of organic material as compared toswitching off the vapor beam of organic material, the distribution pipe208 may also be rotated towards one of the side shields 202 in order toavoid vapor exiting the evaporation source 230 during an operation modewhere vapor emission is not desired.

FIG. 3 depicts an exploded view of one embodiment of the substrate chuck300. The substrate chuck 300 can be a component of the substrate carrier150 a and 150 b. The substrate chuck 300 includes a rigid support base304, an electrode assembly 306 disposed on the rigid support base 304,and an encapsulating member 302 disposed on the electrode assembly 306,which together form the body 311 of the substrate chuck 300. The rigidsupport base 304 defines the bottom surface 312 of the substrate chuck300 while the encapsulating member 302 defines the substrate supportingsurface 313 of the substrate chuck 300. Although not shown, the body 311may include lift pin holes extending there through.

In the embodiment of FIG. 3, the rigid support base 304 has arectangular-like shape having a periphery (defined by the sides 314)that substantially matches the shape and size of electrode assembly 306and encapsulating member 302 to allow the substrates 121 a and 121 bhave a similar shape and size to be secured thereto. It is noted thatthe rigid support base 304, the electrode assembly 306 and theencapsulating member 302 may have an alternative shape or geometryselected as needed to accommodate the geometry of a workpiece, such asthe substrates 121 a and 121 b. For example, although the substratechuck 300 is shown with a rectangular aerial extent, it is contemplatedthat the aerial extent of the substrate chuck 300 may alternatively haveother geometric forms to accommodate different substrates, such ascircular geometric forms to accommodate a circular substrate.

In one embodiment, the rigid support base 304 may be fabricated from aninsulating material, such as a dielectric material or a ceramicmaterial. Suitable examples of the ceramic materials or dielectricmaterials include polymers (i.e., polyimide), silicon oxide, such asquartz or glass, aluminum oxide (Al₂O₃), aluminum nitride (AlN), yttriumcontaining materials, yttrium oxide (Y₂O₃), yttrium-aluminum-garnet(YAG), titanium oxide (TiO), titanium nitride (TiN), silicon carbide(SiC) and the like. Optionally, the rigid support base 304 may be ametal or metallic body having a dielectric layer disposed on the surfaceof the rigid support base 304 facing the electrode assembly 306.

The electrode assembly 306 is disposed on the rigid support base 304 andincludes at least two distributed electrodes 308, 310. Each electrode308, 310 may be charged with different polarities when a chuckingvoltage is applied thereto, thus generating an electrostatic force. Theelectrodes 308, 310 are configured to distribute the electrostatic forcealong a distance at least two times with width of the substrate chuck300. Each electrode 308, 310 may have a plurality of geometric formsinterleaved or interposed among a plurality of geometric forms of theother electrode. As shown in FIG. 3, a plurality of electrode fingers320 comprising electrode 308 are interleaved with plurality of electrodefingers 322 comprising electrode 310. It is believed that theinterleaved fingers 320, 322 of the distributed electrodes 308, 310provides local electrostatic attraction distributed across a large areaof the substrate chuck 300 which in the aggregation provides a highchucking force while using less chucking power. The electrode fingers320, 322 may be formed to have different shapes, lengths and geometry.In one example, one or both of the electrode fingers 320, 322 may beformed from interconnected electrode islands 324. Interconnections 326between electrode islands 324 may be in the plane of the electrodes 308,310 as shown in FIG. 3, or out of plane, such as in the form of jumpersand/or vias. In one embodiment, the electrode finger 320, 322 has awidth 316 of between about 0.25 mm and about 10 mm.

In one embodiment, the electrode assembly 306 may be fabricated from ametallic material, such as aluminum silicon alloy, having a coefficientof thermal expansion similar to the adjacent encapsulating member 302and the rigid support base 304. In one embodiment, the coefficient ofthermal expansion of the electrode assembly 306 is between about 4μm/(m*K) and about 6 μm/(m*K), and is generally within 20 percent of thecoefficient of thermal expansion of the encapsulating member 302.

Between each of the electrode fingers 320 of the first electrode 308,spaces 328 are defined to receive electrode fingers 322 of the secondelectrode 310. The spaces 328 may be an air gap, filled with adielectric spacer material, or filled with at least one of the rigidsupport base 304 or encapsulating member 302.

Vias 332, 334 may be formed through the rigid support base 304 to couplethe first and the second electrodes 308, 310 to the chucking powersource (not shown). In some embodiment, an optional battery 330 may bedisposed in the rigid support base 304 and connected to the first andthe second electrodes 308, 310 by the vias 332, 334 to provide power forchucking the substrates 121 a and 121 b. The battery 330 may be alithium ion battery and may have terminal connections (not shown) on theexterior of the rigid support base 304 for recharging the battery 330without removal from the rigid support base 304.

The encapsulating member 302 is disposed on the rigid support base 304sandwiching the electrode assembly 306, to form the body 311 of thesubstrate chuck 300 as a unitary structure. The encapsulating member 302is positioned on the electrode assembly 306 to provide an insulatingsurface on which the substrates 121 a and 121 b are chucked. Theencapsulating member 302 may be fabricated from a material havingthermal properties, e.g., coefficient of thermal expansion,substantially matching that of the underlying electrode assembly 306. Insome embodiments, the material utilized to fabricate the encapsulatingmember 302 is also utilized to fabricate the rigid support base 304.

After the encapsulating member 302, the electrode assembly 306 and therigid support base 304 are stacked together, a bonding process, such asan annealing process, is performed to fuse the encapsulating member 302,the electrode assembly 306 and the rigid support base 304 together,forming a laminated structure comprising the body 311 of the substratechuck 300. As the encapsulating member 302, the electrode assembly 306and the rigid support base 304 may be required to operate in a hightemperature environment, e.g., greater than 300 degrees Celsius, thematerials utilized to fabricate these three components may be selectedfrom heat resistance materials, such as ceramic materials or glassmaterials, that can sustain high thermal treatment during the annealingprocess. In one embodiment, the encapsulating member 302 and the rigidsupport base 304 may be fabricated from a ceramic material, a glassmaterial, or a composite of ceramic and metal material, providing goodstrength and durability as well as good heat transfer properties. Thematerials selected to fabricate the encapsulating member 302 and therigid support base 304 may have a coefficient of thermal expansion thatis substantially matched to the intermediate electrode assembly 306 toreduce thermal expansion mismatch, which may cause stress or failureunder high thermal loads. In one embodiment, the coefficient of thermalexpansion of the encapsulating member 302 is between about 2 μm/(m*K)and about 8 μm/(m*K). Ceramic materials suitable for fabricating theencapsulating member 302 and the rigid support base 304 may include, butnot limited to, silicon carbide, aluminum nitride, aluminum oxide,yttrium containing materials, yttrium oxide (Y₂O₃),yttrium-aluminum-garnet (YAG), titanium oxide (TiO), or titanium nitride(TiN). In another embodiment, the encapsulating member 302 and the rigidsupport base 304 may be fabricated from a composite material includes adifferent composition of a ceramic and metal, such as metal havingdispersed ceramic particles.

During operation, a charge may be applied to the first electrode 308 andan opposite charge may be applied to the second electrode 310 togenerate an electrostatic force. During chucking, the electrostaticforce generated by the electrodes 308, 310 securely holds the substrates121 a and 121 b to the substrate supporting surface 313 of theencapsulating member 302. As the power supplied from the chucking powersource is turned off, the charges present at the interface 318 betweenthe electrodes 308, 310 may be maintained over a long period of time,thus allowing the substrates 121 a and 121 b to remain chucked to thesubstrate chuck 300 after power has been removed. To release thesubstrate held on the substrate chuck 300, a short pulse of power in theopposite polarity is provided to the electrodes 308, 310 to remove thecharge present in the interface 318.

FIG. 4A depicts a chucking assembly 400, according to one embodiment.The chucking assembly 400 includes a substrate carrier 402 and anelectromagnetic mask chuck 404. The substrate carrier 402 can beconfigured to adhere and release a substrate 420. In one embodiment, thesubstrate carrier 402 is substantially similar to the substrate chuck300, described with reference to FIG. 3.

The electromagnetic mask chuck 404 includes a plurality ofelectromagnets, depicted here as electromagnets 406 a-406 j, containedwithin a chuck body 408. The electromagnets 406 a-406 j each have one ofa plurality of coils 407 wrapped around a core 409. The chuck body 408can completely surround the electromagnets 406 a-406 j. The chuck body408 can further have a support member 410 and a contact surface 412. Thesupport member 410 can position the electromagnetic mask chuck 404 inproximity with the substrate carrier 402. The contact surface 412 is thesurface can rest in contact with the substrate carrier 402. The contactsurface 412 can be a flat surface, as depicted in FIG. 4A.

In one embodiment, the chuck body 408 is fabricated from an insulatingmaterial, such as a dielectric material or a ceramic material. Suitableexamples of the ceramic materials or dielectric materials includepolymers (i.e., polyimide), silicon oxide, such as quartz or glass,aluminum oxide (Al₂O₃), aluminum nitride (AlN), yttrium containingmaterials, yttrium oxide (Y₂O₃), yttrium-aluminum-garnet (YAG), titaniumoxide (TiO), titanium nitride (TiN), silicon carbide (SiC) and the like.Optionally, the chuck body 408 may be a metal or have metallic body. Thechuck body 408 may be a ferromagnetic, ferrimagnetic or non-magneticbody.

The electromagnets 406 a-406 j can have a core composed of aferromagnetic material, such as aluminum-nickel-cobalt (Alnico),Ceramic, Rare-Earth, Iron, Iron-Chromium-Cobalt or combinations thereof.In one embodiment, the electromagnet core is composed of Iron. The core409 is wrapped with the plurality of coils 407. The plurality of coils407 are composed of a conductive material, such as aluminum or copper.The orientation of the plurality of coils 407, and thus the direction ofthe flow of electricity, determines the direction of the polarity of theelectromagnets 406 a-406 j. As such, the electromagnets 406 a-406 j canhave coils which are oriented such that the polarity facing the mask 430alternates from one magnet to the next. Shown here, the north pole ofelectromagnets 406 a, 406 c, 406 e, 406 g and 406 i and the south poleof electromagnets 406 b, 406 d, 406 f, 406 h and 406 j are directedtowards the substrate carrier 402 and the mask 430.

In operation, the substrate 420 is chucked to the substrate carrier 402using an electromagnetic force as described above. A mask 430 ispositioned above and aligned with the substrate 420. The electromagneticmask chuck 404 can be positioned in proximity of the substrate carrier402 in the process chamber in embodiments where the electromagnetic maskchuck 404 is integrated with the process chamber. In other embodiments,the electromagnetic mask chuck 404 is integrated with the substratecarrier 402. In either embodiment, the power source activates theelectromagnets in the electromagnetic mask chuck 404 such that amagnetic field is generated and delivered to the mask 430. Theelectromagnetic mask chuck 404 receives an electric charge from a powersource 416 which is delivered through a connection 414 to each of theplurality of coils 407. The electromagnetic mask chuck 404 then providesa magnetic field with a strength commensurate with the electricityprovided to the plurality of coils 407, up to the saturation point ofthe material, to the mask 430. The saturation point of the material isrelated to the quantity and type of material used as the core 409. Themagnetic force from the electromagnets 406 a-406 j in theelectromagnetic mask chuck 404 brings at least a portion of the mask 430into position over or in contact with the substrate 420. A layer (notshown) is then deposited through the mask 430 on the substrate 420. Oncethe layer is deposited, the electrical flow from the power source 416 tothe electromagnetic mask chuck 404 is stopped, thereby stopping theproduction of a magnetic field.

The electromagnetic mask chuck 404 is depicted here as a rectangularshape. However, the electromagnetic mask chuck 404 can be of any shapesuch that it can deliver the magnetic field of the electromagnets 406a-406 j to the mask 430.

FIG. 4B-4E depict further embodiments of an electromagnetic mask chuckuseable with a chucking assembly, according to embodiments describedherein. The magnetic field strength delivered to the mask 430 is basedin part on the position of the plurality of electromagnets, the size ofthe core of the electromagnet and the power delivered to the coils.Thus, in the embodiments below, the position of the electromagnet, thesize of the electromagnet, power levels delivered to the coils of theelectromagnet and combinations thereof are applied to control themagnetic field strength applied to different portions of the mask 430.

FIG. 4B depicts a top view of an electromagnetic mask chuck 440 withmultiple rectangular cores, according to an embodiment. Theelectromagnetic mask chuck 440 has a chuck body 442. The chuck body 442can be composed of similar materials to those described with referenceto FIG. 4A. Positioned in the chuck body 442 are a plurality ofelectromagnets 444, shown here as fourteen (14) electromagnets 444having an approximately equal size. The specific number ofelectromagnets can be increased or decreased to fit the needs of theuser. The electromagnets 444 include a core 446 and a coil 448 wrappedaround the core. In this embodiment, the coil 448 is wrapped around thecore 446 lengthwise, creating an elongated rectangular shape. Theplurality of electromagnets 444 are positioned such that the magneticfield is delivered in horizontal rows, with alternating poles, as shownin more detail in FIG. 4A. In this embodiment, the strength of themagnetic field is controlled by the amount of power delivered from thepower source 416.

In operation, the mask 430 is positioned above and aligned with thesubstrate 420 as described with reference to FIG. 4A. The coils 448 ofthe electromagnetic mask chuck 440 then receive electricity from thepower source 416. The electricity creates a magnetic field in the coilswhich, in conjunction with the field created in the core 446, delivers amagnetic field to the mask 430. The electromagnetic mask chuck 440 canbe positioned and deliver a magnetic field as described with referenceto FIG. 4A when integrated with the process chamber or when integratedwith the substrate carrier 402. The magnetic force from theelectromagnets 444 in the electromagnetic mask chuck 440 brings at leasta portion of the mask 430 into position over or in contact with thesubstrate 420. The plurality of electromagnets 444 can deliver themagnetic field with a controlled magnetic field strength such that aportion of the mask 430 can be positioned sequentially, simultaneously,in a random order or any variation of sequence. Sequential as used hereis with relation to the electromagnet 444 in the highest position asshown in the graphic and each subsequent electromagnet 444 in sequence.

This design is believed to have a protective effect on the substrate420, reducing the force of contact with the mask 430. As the magneticfield strength can be precisely controlled in an electromagnet, e.g. theplurality of electromagnets 444, a portion of the mask 430 can bebrought into position over the substrate 420 in a more controlled andnon-mechanical manner. In one embodiment, first electromagnet of theelectromagnets 444 can apply a greater magnetic field strength on themask 430 than each subsequent electromagnet, allowing for a more gradualoverall connection.

FIG. 4C depicts a top view of an electromagnetic mask chuck 440 withmultiple angled rectangular cores, according to an embodiment. Theelectromagnetic mask chuck 450 has a chuck body 452. The chuck body 452can be composed of similar materials to those described with referenceto FIG. 4A. Positioned in the chuck body 452 are a plurality ofelectromagnets 454, shown here as twenty (20) electromagnets 454 with asize commensurate with the available space in the chuck body 452. Thespecific number of electromagnets 454 can be increased or decreased tofit the needs of the user and the available size. The electromagnets 454include a core 456 and a coil 458 wrapped around the core. In thisembodiment, the coil 458 is wrapped around the core 456 lengthwise,creating shapes from a square-like shape to an elongated rectangularshape. The plurality of electromagnets 444 are positioned such that themagnetic field is delivered in horizontal rows, with alternating poles,as shown in more detail in FIG. 4A. In this embodiment, the strength ofthe magnetic field is controlled by the amount of power delivered fromthe power source 416. Each of the magnets can be connected to the samepower source, to a separate power source, or to a regulated power sourcesuch that the electricity can be delivered unequally to the coils 458.

In operation, the mask 430 is positioned above and aligned with thesubstrate 420 as described with reference to FIG. 4A. The coils 458 ofthe electromagnetic mask chuck 450 then receive electricity from thepower source 416. The electricity creates a magnetic field in the coils458 which, in conjunction with the field created in the core 456,delivers a magnetic field to the mask 430. The electromagnetic maskchuck 450 can be positioned and deliver a magnetic field as describedwith reference to FIG. 4A when integrated with the process chamber orwhen integrated with the substrate carrier 402. The magnetic force fromthe electromagnets 454 in the electromagnetic mask chuck 450 brings atleast a portion of the mask 430 into position over or in contact withthe substrate 420. The plurality of electromagnets 454 can deliver themagnetic field with a controlled magnetic field strength such that aportion of the mask 430 can be positioned sequentially, simultaneously,in a random order or any variation of sequence.

This design is believed to have a protective effect on the substrate420, spreading the force of contact with the mask 430 over a largerarea. As above, the magnetic field strength is a function of theelectricity delivered to the electromagnet 454, the electromagnets 454receive electricity to sequentially apply the magnetic field in anangled fashion. Thus, the strength of the magnetic field applied to themask 430 will gradually increase toward the center as the electromagnets454 are sequentially larger. This spread of magnetic field will allowfor a more gradual overall connection.

FIG. 4D depicts a top view of an electromagnetic mask chuck 440 withmultiple circular cores, according to an embodiment. The electromagneticmask chuck 460 has a chuck body 462. The chuck body 462 can be composedof similar materials to those described with reference to FIG. 4A.Positioned in the chuck body 462 is a plurality of electromagnets 464,shown here as 242 electromagnets 464 with a size commensurate with theavailable space in the chuck body 462. The specific number ofelectromagnets 464 can be increased or decreased to fit the needs of theuser and the available size. The electromagnets 464 include a core 466and a coil 468 wrapped around the core 466. In this embodiment, the coil468 is wrapped around the core 466 lengthwise, creating a plurality ofcircular shapes. The plurality of electromagnets 464 are positioned suchthat the magnetic field is delivered in a more targeted fashion, withalternating poles, as shown in more detail in FIG. 4A. In thisembodiment, the strength of the magnetic field is controlled by theamount of power delivered from the power source 416. Each of the magnetscan be connected to the same power source, to a separate power source,or to a regulated power source such that the electricity can bedelivered unequally to the coils 468.

In operation, the mask 430 is positioned above and aligned with thesubstrate 420 as described with reference to FIG. 4A. The coils 468 ofthe electromagnetic mask chuck 460 then receive electricity from thepower source 416. The electricity creates a magnetic field in the coils468 which, in conjunction with the field created in the core 466,delivers a magnetic field to the mask 430. The electromagnetic maskchuck 460 can be positioned and deliver a magnetic field as describedwith reference to FIG. 4A when integrated with the process chamber orwhen integrated with the substrate carrier 402. The magnetic force fromthe electromagnets 464 in the electromagnetic mask chuck 460 brings atleast a portion of the mask 430 into position over or in contact withthe substrate 420. The plurality of electromagnets 464 can deliver themagnetic field with a controlled magnetic field strength such that aportion of the mask 430 can be positioned sequentially, simultaneously,in a random order or any variation of sequence. The positioning of theelectromagnets 464 allow for more targeted application of the magneticfield as the fields can be created more individually.

This design is believed to have a protective effect on the substrate420, spreading the force of contact with the mask 430 over a largerarea. As above, the magnetic field strength is controllable based on theelectricity delivered. The electromagnets 464 are sized to sequentiallyapply the magnetic field in any order or shape while also controllingthe strength of the magnetic field from each. Thus, the strength of themagnetic field applied to the mask 430 can be independently controlledas the electromagnets 464 sequentially enter range to apply their fieldto the mask 430. This spread of magnetic field will allow for a moregradual overall connection.

FIG. 4E depicts a top view of an electromagnetic mask chuck 440 withmultiple rectangular cores, according to an embodiment. Theelectromagnetic mask chuck 470 has a chuck body 472. The chuck body 472can be composed of similar materials to those described with referenceto FIG. 4A. Positioned in the chuck body 472 is a plurality ofelectromagnets 474, shown here as 168 electromagnets 474 with a sizecommensurate with the available space in the chuck body 472. Thespecific number of electromagnets 474 can be increased or decreased tofit the needs of the user and the available size. The electromagnets 474include a core 476 and a coil 478 wrapped around the core 476. In thisembodiment, the coil 478 is wrapped around the core 476 lengthwise,creating a plurality of square or rectangular shapes. The plurality ofelectromagnets 474 are positioned such that the magnetic field isdelivered in a more targeted fashion, with alternating poles, as shownin more detail in FIG. 4A. In this embodiment, the strength of themagnetic field is controlled by the amount of power delivered from thepower source 416. Each of the electromagnets 474 can be connected to thesame power source, to a separate power source, or to a regulated powersource such that the electricity can be delivered unequally to the coils478.

In operation, the mask 430 is positioned above and aligned with thesubstrate 420 as described with reference to FIG. 4A. The coils 478 ofthe electromagnetic mask chuck 470 then receive electricity from thepower source 416. The electricity creates a magnetic field in the coils478 which, in conjunction with the field created in the core 476,delivers a magnetic field to the mask 430. The electromagnetic maskchuck 470 can be positioned and deliver a magnetic field as describedwith reference to FIG. 4A when integrated with the process chamber orwhen integrated with the substrate carrier 402. The magnetic force fromthe electromagnets 474 in the electromagnetic mask chuck 460 brings atleast a portion of the mask 430 into position over or in contact withthe substrate 420. The plurality of electromagnets 474 can deliver themagnetic field with a controlled magnetic field strength such that aportion of the mask 430 can be positioned sequentially, simultaneously,in a random order or any variation of sequence. The positioning of theelectromagnets 474 allow for more targeted application of the magneticfield as the fields can be created more individually.

In the exemplary embodiments described above, the electromagnets arepositioned such that the distance of the electromagnets from the mask430 is approximately equal. However, the magnetic field from a magnet isinversely proportional to approximately the cube of the distance fromthat object. As such, the electromagnets may be positioned at a varietyof distances to further control the magnetic field delivered to the mask430. Further, the three dimensional positioning of the electromagnetsneed not be uniform. It is contemplated that the magnets can be in avariety of shapes and positions, either with a distinct pattern,positioned randomly or combinations thereof.

Thus the position, size and power received of the electromagnetsemployed in the electromagnetic mask chuck creates a magnetic field tomove the mask into position over the substrate for a deposition process.By controlling the size and proximity of and electricity delivered tothe electromagnets, the magnetic field can be applied to safely andsecurely to chuck and release the mask as needed during a depositionoperation.

In one embodiment, a processing system is described. The processingsystem can include a process chamber (e.g., the vacuum chamber 110)configured to receive a substrate carrier holding a substrate, and todeposit a material on the substrate while on the substrate carrier. Theprocessing system can further include an electromagnetic mask chuck(e.g., electromagnetic mask chuck 440, 450, 460) positioned in theprocess chamber. The electromagnetic mask chuck can include a pluralityof electromagnets (e.g., electromagnets 406 a-406 j) operable to chuck amask to the substrate through the substrate carrier.

The processing system can further include the electromagnetic mask chuckbeing operable to sequential increase a magnetic field from theplurality of electromagnets.

The processing system can further include the electromagnetic mask chuckbeing operable to generate more force in a center region of theelectromagnetic mask chuck relative to a peripheral region of theelectromagnetic mask chuck.

The processing system can further include the electromagnetic mask chuckbeing operable to generate more force on one side of the electromagneticmask chuck relative to an opposite side of the electromagnetic maskchuck.

The processing system can further include a first electromagnet of theplurality of electromagnets being configured to deliver a magnetic fieldhaving a strength different than a second electromagnet.

The processing system can further include the plurality ofelectromagnets being independently controllable.

The processing system can further include the plurality ofelectromagnets being each configured to produce a magnetic field withunequal strength as compared between them, such that one portion of themask is pulled with more force than another proportion of the mask.

In another embodiment, a substrate carrier (e.g., substrate carrier 150a and 150 b) for use in a process chamber is described. The substratecarrier can include a support base (e.g., support base 304) configuredto transport a substrate (e.g., a first substrate 121 a and a secondsubstrate 121 b) into and out of the processing chamber, the supportbase having a substrate supporting surface (e.g., substrate supportingsurface 313). The substrate carrier can further include anelectromagnetic mask chuck coupled to the support base, Theelectromagnetic mask chuck can include a plurality of electromagnetsoperable to chuck a mask to the substrate through the substrate carrier.

The substrate carrier can further include the plurality ofelectromagnets being positioned equidistant from the substratesupporting surface.

The substrate carrier can further include a distance between theelectromagnets and the substrate supporting surface which varies.

The substrate carrier can further include the plurality ofelectromagnets being rectangular magnets.

The substrate carrier can further include the electromagnets beingindependently controllable.

The substrate carrier can further include the electromagnetic mask chuckbeing operable to sequentially increase a magnetic field from theplurality of electromagnets.

The substrate carrier can further include a power source coupled to theplurality of electromagnets.

The substrate carrier can further include the chuck body including aceramic material.

In another embodiment, a method for chucking a mask in a process chamberis described. The method can include transferring a substrate disposedon a substrate supporting surface of a substrate carrier into a processchamber. The substrate carrier can then be positioned in a processingposition within the process chamber. Then, a mask is electromagneticallychucked to the substrate disposed on the substrate carrier.Subsequently, a layer of material, such as an organic material suitablefor OLED fabrication, is deposited through the mask onto the substrate.

Electromagnetically chucking the mask to the substrate can furtherinclude chucking the mask to the substrate in a center to edge sequence.Electromagnetically chucking the mask to the substrate can furtherinclude chucking the mask to the substrate in a first edge to secondedge sequence. Electromagnetically chucking the mask to the substratecan further include independently controlling force generated by aplurality of electromagnets disposed in the process chamber.Transferring the substrate disposed the substrate carrier into theprocess chamber can further include moving the electromagnets into theprocess chamber.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A processing system comprising: a process chamberconfigured to deposit a material on the substrate; a carrier positioningelement disposed in the process chamber, the carrier positioning elementconfigured to receive and position a removable substrate carrier in theprocess chamber; and an electromagnetic mask chuck positioned in theprocess chamber, aligned with the carrier positioning element, theelectromagnetic mask chuck comprising: a plurality of electromagnetsoperable to chuck a mask to the substrate on the substrate carrierthrough the substrate carrier; and a power source coupled to theplurality of electromagnets.
 2. The processing system of claim 1,wherein the electromagnetic mask chuck is operable to sequentialincrease a magnetic field from the plurality of electromagnets.
 3. Theprocessing system of claim 2, wherein the electromagnetic mask chuck isoperable to generate more force in a center region of theelectromagnetic mask chuck relative to a peripheral region of theelectromagnetic mask chuck.
 4. The processing system of claim 2, whereinthe electromagnetic mask chuck is operable to generate more force on oneside of the electromagnetic mask chuck relative to an opposite side ofthe electromagnetic mask chuck.
 5. The processing system of claim 1,wherein a first electromagnet of the plurality of electromagnets isconfigured to deliver a magnetic field having a strength different thana second electromagnet.
 6. The processing system of claim 1, wherein theplurality of electromagnets are independently controllable.
 7. Theprocessing system of claim 1, wherein the plurality of electromagnetsare each configured to produce a magnetic field with unequal strength ascompared between them, such that one portion of the mask is pulled withmore force than another proportion of the mask.
 8. A substrate carrierfor use in a process chamber, the substrate carrier comprising: asupport base configured to transport a substrate into and out of theprocessing chamber, the support base having a substrate supportingsurface and a plurality of electrodes operable to hold a substrate tothe substrate supporting surface; and an electromagnetic mask chuckcoupled to the support base, the electromagnetic mask chuck comprising aplurality of electromagnets operable to chuck a mask to the substratethrough the substrate carrier.
 9. The substrate carrier of claim 8,wherein the plurality of electromagnets are positioned equidistant fromthe substrate supporting surface.
 10. The substrate carrier of claim 8,wherein a distance between the electromagnets and the substratesupporting surface varies.
 11. The substrate carrier of claim 8, whereinthe plurality of electromagnets are rectangular magnets.
 12. Thesubstrate carrier of claim 8, wherein the electromagnets areindependently controllable.
 13. The substrate carrier of claim 8,wherein the electromagnetic mask chuck is operable to sequentiallyincrease a magnetic field from the plurality of electromagnets.
 14. Thesubstrate carrier of claim 8, further comprising a power source coupledto the plurality of electromagnets.
 15. The substrate carrier of claim12, wherein the chuck body comprises a ceramic material.